1. Field of Invention
A new optical concept for parabolic reflector design, which converts a line source or sink into a point source and sink, and its related applications.
2. Description of Prior Art
Parabolic reflectors have been used up to this date as an efficient means of converting a parallel beam of radiation to a point known as the focal point of the reflector. This is the way the radar antenna, microwave dish, long range telescopes and search lights are designed. To produce a high quality beam, a point source theoretically with no physical dimension should be placed at the focal point of the parabolic reflector. To enlarge an image or to shrink the image down, the smallness of the point source and the intensity of the source trades off with power input capability, and flux density with materials due primarily to heat. With the search light, the limitation is the electric arc spot size and current density. For other light sources, tungsten filament lamps are limited by the melting temperature of tungsten and the filament length. Spark sources can be better than most point sources but cannot be a continuous source; besides, the source still has a finite dimension. For optical calibration and other high resolution projection and detection, a point source is being filtered by spatial filters such as a pin hole. This cuts down the intensity of the source and still has the resolution limited by the dimension of the pin hole. From the detection point of view, the dimension of the linear array of detectors operating in-phase will be better than a single detector collecting signals at a point source, which will make it very difficult to single out signal from white noises. All this is due to the limitations of the traditional parabolic geometry. The perfect parabolic reflector can be described by the parametric equation y.sup.2 =4px, then rotated about the X-axis. Here p is the distance from the focal point to the bottom of the dish, and 2p will be radius from the focal point perpendicular to the X-axis. This geometry is what many optical devices are based on, with variations and perturbations, depending on applications. With this limitation, the future progress has been limited in many areas. For example: 1) the optical resolution of the light sources limits the line width of lithography when used to shrink printed circuit to a micro chip; 2) the optical resolution limits the resolution of shadowgraph when used to photograph aerodynamic flows; 3) the optical resolution limits the distance of search light and radar range; 4) in a movie projector, the arc spot intensity limits the screen size of a given negative size to still retain resolution and visibility; 5) the slide projector has an intense halogen lamp located at the focal point of a deep parabolic reflector, etc.
It is possible to make a source in a linear form such that the intensity locally can still be limited by material properties; however, the total intensity will be integrated along the linear source. This is not possible with the traditional parabolic reflectors. When such a need appears, a bank of parabolic reflectors each with its own point source or detectors are seen either as radar antenna farms or search light banks, each one still limited by their own resolution and intensity problems.
The following description of the newly invented Cheng Orthogonal Parabolic Reflector will overcome those problems and opens new applications hitherto unthinkable by designers.